VPN problem - problems with "no buffer space available"

I know this is not new problem and I can find many posts here about it, but still there is no available solution.

When I connect to VPN (PPTP) from my Mac, after short time there is no connection to the Internet. It works 2-3 minutes and then crash.

When I ping any IP, after that time there is message: "no buffer space available".
When I use PC with Windows, everything is fine and connection is established for the whole day.

Is anybody who knows how to solve this problem???

PING 172.16.1.10 (172.16.1.10): 56 data bytes
64 bytes from 172.16.1.10: icmp_seq=3 ttl=128 time=36.268 ms
64 bytes from 172.16.1.10: icmp_seq=4 ttl=128 time=44.690 ms
64 bytes from 172.16.1.10: icmp_seq=5 ttl=128 time=47.108 ms
64 bytes from 172.16.1.10: icmp_seq=6 ttl=128 time=34.294 ms
64 bytes from 172.16.1.10: icmp_seq=7 ttl=128 time=39.272 ms
64 bytes from 172.16.1.10: icmp_seq=8 ttl=128 time=866.299 ms
64 bytes from 172.16.1.10: icmp_seq=9 ttl=128 time=54.931 ms
64 bytes from 172.16.1.10: icmp_seq=10 ttl=128 time=1864.334 ms
64 bytes from 172.16.1.10: icmp_seq=11 ttl=128 time=24869.021 ms
64 bytes from 172.16.1.10: icmp_seq=12 ttl=128 time=25867.907 ms
64 bytes from 172.16.1.10: icmp_seq=13 ttl=128 time=25867.758 ms
64 bytes from 172.16.1.10: icmp_seq=14 ttl=128 time=25907.162 ms
64 bytes from 172.16.1.10: icmp_seq=15 ttl=128 time=26867.447 ms
64 bytes from 172.16.1.10: icmp_seq=16 ttl=128 time=26883.072 ms
ping: sendto: No buffer space available
64 bytes from 172.16.1.10: icmp_seq=17 ttl=128 time=27879.732 ms
64 bytes from 172.16.1.10: icmp_seq=18 ttl=128 time=27886.523 ms
64 bytes from 172.16.1.10: icmp_seq=19 ttl=128 time=27876.230 ms
ping: sendto: No buffer space available
ping: sendto: No buffer space available
ping: sendto: No buffer space available
ping: sendto: No buffer space available
ping: sendto: No buffer space available
ping: sendto: No buffer space available
etc.


Best regards,
Marek